The invention relates in general to optical lenses, and in particular to optical lenses with high structural strength and high stability for injection molding.
Optical glass and optical plastic are two major materials used in optical lens fabrication. As optical plastic materials are cheap and easy to produce, they have been widely applied in various productions of optical lenses.
Referring to FIG. 1, a conventional plastic optical lens is formed by injection molding, and comprises a round main body M surrounded by a flange F. The main body M, such as an aspherical optical lens, refracts light to alter the optical path. The flange F sustains and connects other optical lenses. An annular depression R is formed between the main body M and the flange F, symmetrical to a central axis C of the main body M.
As shown in FIG. 1, to produce a conventional plastic optical lens, plastic resin is injected into a mold (not shown) through a gate G along the first direction A1, wherein the width of the gate G is d1. As the plastic resin moves to a narrow region of width d2 (d2<d1) adjacent to the depression R, the resin can thicken and become sluggish and unstable, leading to possible surface imperfections and incomplete filling of the mold.